This was definitely the best episode of the crossover. Overall though, I'm not particularly impressed.
It was nice seeing Oliver, Barry and Kara hang out, but I do sense some sort of awkwardness between Stephen Amell and Melissa Benoist. The other interactions were all great though.
I laughed a lot at Superman thinking Cisco was Kara. Hilarious. Clark is awesome and Tyler Hoechlin is great. It would be really fun to add a Superman series to the Arrowverse.
Kate Kane's cameo at the end was so pointless. Really unimpressed with her.
I don't think Oliver made some massive sacrifice to The Monitor. For starters, Oliver is supposed to be alive in the flash forwards on Arrow (at least, no one has mentioned that he is dead). Also, if Oliver did make some big sacrifice, then Stephen Amell played it atrociously post-sacrifice.
I feel like this crossover could have felt bigger, but it didn't. If next years crossover, which seems to be a massive deal, is done in the same format as this one, I'm not going to be impressed.
Kara, Barry and Superman were definitely the highlights overall. Also, more Iris next year!

I thought The Flash episode was better, but this wasn't bad. I definitely feel like there is some awkwardness between Oliver and Kara, she feels far more comfortable with Barry. I suppose Melissa Benoist and Grant Gustin have more history and have spent more time together than she has with Stephen Amell. Not to say that there interactions in the crossover aren't decent, but they could be better. It might be worth hanging out more off set maybe to build a better rapport?
Highly unimpressed with Kate Kane. She just seems so stiff. I know nothing about the comic character, is she supposed to be like this? I would have thought, as the announcement of the Batwoman show was such a big deal, that she would be someone more charismatic. Unless it's the actress, in which case Kate Kane is terribly miscast.
I find it amusing that Dinah wasn't in the episode, considering how much screen time she has been getting this season of Arrow. This is not a complaint about this episode!
Is it me, or does Oliver's voice go all high when he attempts comedy? It's a bit strange.

Overall, it wasn't bad.
I don't think we have ever seen Oliver laugh like that ever, which was interesting to see. Not sure how well it played though. I think Barry worked far better as the Green Arrow than Oliver did as The Flash. I do find it odd that the only way to be one or the other is to be filled with happiness or darkness for The Flash and Green Arrow respectively. I rolled my eyes at that.
Sherloque is so irritating, probably one of the most irritating characters in the Arrowverse along with Curtis on Arrow.
I also think Kara works far better with Barry than with Oliver. The actors seem more comfortable too.
Superman was great, Lois felt a bit pointless.
LOVED hearing the Smallville theme tune. That brought back memories.